Forging refers to a workpiece or blank obtained by forging and deforming a metal blank. By applying pressure to the metal blank, it produces plastic deformation, which can change its mechanical properties. According to the temperature of the blank during processing, forgings can be divided into cold forging and warm forging and hot forging. Cold forging is generally processed at room temperature, and hot forging is processed at a temperature higher than the recrystallization temperature of the metal blank.
The preparation before forging includes raw material selection, calculation, blanking, heating, calculation of deformation force, selection of equipment, and design of molds. It is necessary to choose a good lubrication method and lubricant before forging.
Forging materials involve a wide range, including steel and high-temperature alloys of various grades, as well as non-ferrous metals such as aluminum, magnesium, titanium, copper, etc.; there are both bars and profiles processed into different sizes at one time, and a variety of Ingots with specifications; in addition to using a large number of domestic materials suitable for my country's resources, there are also materials from abroad.

Forging

Most of the forged materials are listed in national standards, and many are new materials developed, tried and promoted. As we all know, the quality of products is often closely related to the quality of raw materials. Therefore, for forging workers, they must have the necessary material knowledge and be good at selecting the most suitable materials according to the process requirements.

Material calculation and blanking are one of the important links to improve material utilization and realize blank refinement. Too much material not only causes waste, but also aggravates cavity wear and energy consumption. If the blanking does not leave a margin, it will increase the difficulty of process adjustment and increase the scrap rate. In addition, the quality of the blanking end face also has an impact on the process and the quality of cylindrical forgings.
The purpose of heating is to reduce forging deformation force and improve metal plasticity. But heating also brings a series of problems, such as oxidation, decarburization, overheating and overburning. Accurate control of the initial forging and final forging temperature has a great influence on the product structure and performance. Flame furnace heating has the advantages of low cost and strong applicability. However, the heating time is long, oxidation and decarburization are prone to occur, and the working conditions need to be continuously improved. Electric induction heating has the advantages of rapid heating and less oxidation, but it has poor adaptability to product shape, size and material changes.
Forging forming is produced under the action of external force. Therefore, correct calculation of deformation force is the basis for selecting equipment and checking mold. The stress and strain analysis inside the deformed body is also indispensable for optimizing the process and controlling the structure and performance of the forging.
There are four main methods for analyzing deformation force. Although the principal stress method is not very strict, it is relatively simple and intuitive. It can calculate the total pressure and the stress distribution on the contact surface of the workpiece and the tool. The slip line method is strict for the plane strain problem. It is relatively intuitive to solve the stress distribution for the local deformation of high parts, but the scope of application is narrow.

Forging

The upper limit method can give an overestimated load, and the upper limit element can also predict the shape change of the workpiece during deformation. The finite element method can not only give the external load and the change of the workpiece shape, but also the internal stress and strain distribution. The disadvantage is that the computer time is more, especially when the elastoplastic finite element is used to solve the problem, the computer capacity is larger. The machine time is longer. Recently, there is a trend to adopt a joint method to analyze problems, for example. The upper limit method is used for rough calculation, and the finite element is used for detailed calculation in key parts.

Reducing friction can not only save energy, but also increase the die life of forgings. Since the deformation is relatively uniform, it helps to improve the structure and performance of the product. One of the important measures to reduce friction is to use lubrication. Due to the different forging methods and the difference in working temperature, the lubricants used are also different. Glass lubricants are mostly used for forging of high-temperature alloys and titanium alloys. For hot forging of steel, water-based graphite is a widely used lubricant. For cold forging, due to the high pressure, phosphate or oxalate treatment is often required before forging.

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